328 The Journal 
It may be argued that temperature 
or some other factor due to an advancing 
season was the effective stimulus rather 
than the removal of parts but this makes 
little difference as it would still be an 
external stimulus. The same statement 
may be made with regard to the possible 
effects of chemicals and diminished light 
intensity. However, the percentage of 
monoeciousness was determined on sey- 
eral successive dates in two neighboring 
fields designated respectively as A and 
B. These results are presented in 
Table I. 
The percentage of monoecious. plants 
in field A was much larger than in field 
B. This may have been due to wider 
spacing, as the plants in field A stood 
farther apart than in field B and 
consequently were larger and better fed; 
or it may have been caused by some 
inherent difference in the seed. 
If we exclude the records of late 
maturing plants, made on October 1, the 
table shows no evidence of an increased 
percentage of monoeciousness as the 
season advanced. 
The results for 1914 are presented in 
Table II. As they show unmistakeable 
evidence of sex alteration from the use 
of external stimuli they are published 
in detail. Both the number and char- 
acter of flowers removed as well as those 
that subsequently developed are in- 
cluded. 
As shown by the table, sex was not 
altered by bagging the tops but was 
very decidedly altered by the removal 
of flowers. Of the fourteen male plants 
that formed flowers after the operation 
only three developed pistils but every 
female plant produced both stamens 
and pistils in abundance. In fact the 
proportion of stamen-bearing flowers 
formed on female plants greatly excceds 
that ordinarily formed on monoecious 
plants. 
As a check on the experiments re- 
corded in Table II, twenty-eight female 
plants were tagged at the time of the 
foregoing operations and carefully ex- 
amined at the end ot the season for the 
appearance of male sex organs but not 
a single stamen had developed. 
It is evident from the experiments 
and their checks that changes in sex 
of Heredity 
were induced by the removal of flowers 
and flower buds, probably through 
alteration of the food supply. The 
production of pollen and ovules is an 
exhausting process. As soon as male 
hemp plants shed their pollen they turn 
yellow and die. The removal of flowers 
and flower buds from the female plants 
when their reserve food is at a minimum 
probably makes the nutritive conditions 
less favorable for the development of 
the new buds and in accordance with 
the food theory of sex determination, 
causes an excess of male development. 
The appearance of pistillate flowers upon 
a few treated male plants, however, is 
difficult to explain upon this basis unless 
we assume that these particular flowers 
received more than their share of the 
food supply. 
If the effect of flower removal on the 
food supply has been properly inter- 
preted, it is evident that the proper 
method of inducing pistillate develop- 
ment in male plants is through high 
feeding, especially about the time of 
flower formation. This should be done 
through the soil in such a way as not to 
interfere with the plants’ normal physio- 
logical activities. 
CONCLUSIONS 
The foregoing experiments show that 
sex of hemp is alterable by the removal 
of flowers. While only a few male 
plants produced pistils, they constituted 
14 to 21% of the total number of males 
reproducing flowers after the operation. 
It is quite probable that if the proper 
stimulus were used pistil formation 
could be induced in all the males. The 
females were very responsive to _the 
stimulating effect of flower removal. 
In fact in the second year’s experiments 
every female operated upon produced 
an abundance of stamens. 
The results do not seem to support 
the theory that sex is wholly a matter of 
zygotic constitution—one dose or 
amount of an inherited sex factor 
producing one sex and two the other, 
but indicate that both males and 
females are potential hermaphrodites as 
believed by Darwin and Strasburger. 
